Fix tools/ci/tox script when 'python' command is not available

Change-Id: I73f5b45de60f47a489a8140ab63baa899599e34e

tools/ci/activate

@@ -20,7 +20,8 @@ function get_realpath {
             local script=$("${python}" "${script}" "${script}")
             echo "${python}" "${script}"
         else
-            which realpath
+            echo "Python command not found!" 1>&2
+            exit 1
         fi
     )
 }

tools/ci/tox

@@ -103,7 +103,7 @@ function tox_install_bindeps {
     local missing_packages=( $(bindep -b -f "${bindep_file}") )
     if [ "${#missing_packages[@]}" != "0" ]; then
         tox_install_packages "${missing_packages[@]}"
-        "${BINDEP}" -f "${bindep_file}"
+        bindep -f "${bindep_file}"
     fi
 }